從頸動脈橫切面及縱剖面之超音波動態影像以非線性分析方法評估其彈性

Nonlinear Analysis of Carotid Artery Distensibility from Transverse and Longitudinal Views of Dynamic Ultrasound Imaging

陳震霖(Chen-Lin Chen)

指導教授 ： 劉偉名

國立中正大學/工學院/資訊工程學系/碩士(2015年)

摘要

衛生署福利部指出心血管疾病是台灣與全球的主要死因，且每年死亡人數逐漸增加。大部分心血管疾病的病因都與動脈硬化有密切關聯。動脈硬化有好發的部位，而頸動脈就是其中之一，頸動脈是血液流向大腦的主要管道，其硬化可能會造成腦中風，是預防動脈硬化的重點部位。
超音波影像可檢查頸動脈管壁病變狀況，是一種便宜又無危險性的方式。許多局部性評估動脈硬化方法是計算血管的管腔與血壓在收縮與舒張期之間變化的比值，這類方法有許多因素影響其正確性。近似熵與交叉近似熵這些非線性分析法已被用於多種生理訊號，做為判斷正常與異常的指標。目前已有研究利用近似熵分析頸動脈長時間變化資訊做為動脈彈性的判斷。我們的目在於實驗不同影像分割方法下的頸動脈長時間變化結果，檢驗有哪些變因會影響非線性分析法的判斷，並探討非線性分析法評估結果是否可明確的指出正常與不正常的頸動脈之間差異。
實驗結果顯示受試者的心跳速率會影響近似熵的評估，在沒有心跳速率影響情況下近似熵分析可以明確指出正常與有硬化頸動脈兩族群間的差異；交叉近似熵則不受心跳速率影響，也能明確的指出是否硬化這兩族群間的差異。這二種非線性分析法不會因不同影像分割法的頸動脈長時間變化資訊結果而造成評估錯誤。

關鍵字

交叉近似熵 ； 近似熵 ； 超音波影像 ； 動脈彈性 ； 頸動脈硬化

並列摘要

Ministry of Health and Welfare showed that the main cause of death in Taiwan and around the world is cardiovascular disease, and the resulted number of death is increasing. Most cardiovascular diseases are closely related to atherosclerosis. Since the carotid is the main blood supply channel to the brain, its atherosclerosis will cause stroke and is worthy of monitoring.
Ultrasound imaging is a cheap and risk-free method to examine the carotid wall for any abnormality. Most methods for estimating the carotid stiffness is to calculate the ratio of lumen diameter (area) and blood pressure between the systolic and diastolic period, but the accuracy and stability would be influenced by many factors. Some studies showed that the stiffness can be assessed by calculating the approximate entropy (ApEn) of that long-term cross section change of carotid. The ApEn and cross-ApEn are nonlinear analysis methods that have been used to analyze many kinds of physiological signals to distinguish abnormality from the normal states. Our goals are two-folded. The first is to verify if the nonlinear analysis results of long term carotid diameter change will be influenced by different image segmentation methods or other factors. The second is to evaluate if the nonlinear analysis can make significant difference between normal and abnormal carotid movements.
Our experimental results show that both ApEn and cross-ApEn can make significant difference between normal subjects and carotid atherosclerosis patients, but ApEn will be biased by the heart rate. It works only when the heart rate is normalized before comparisons between groups. Different image segmentation methods will not deviate both entropy calculations.

並列關鍵字

Ultrasound imaging ； Cross approximate entropy ； Distensibility ； Arteriosclerosis ； Carotid artery

參考文獻

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